Human leukocyte antigen (HLA) genes are the most polymorphic genes in the human genome. Knowledge about HLA polymorphism in relation to possible peptide-based, T-cell-restricted vaccination protocols is important for understanding the physiology of T-cell recognition and to improve strategies of T-cell antigen-specific vaccination. During the last few years the HLA Laboratory has developed and perfected techniques for high-resolution typing of HLA class I and class II molecules using polymerase chain reaction (PCR) techniques and more recently robotic sequencing. With these high-resolution methods it has been possible to achieve several categories of results: Development of antigen identification program based on co-transfection of HLA and cDNA libraries into permissive antigen presenting cells (in this fashion a new epitope for anti-cancer treatment was identified this year in our lab). Development of a technology for the preparation of epitope/HLA tetrameric complexes for various HLA alleles and various minimal epitopic sequences that can be used for patient monitoring during vaccination as well as sorting of relevant antigen-specific T-cells. Preparation of a cDNA library of various HLA alleles to be readily available to our lab and the community at large for the previously mentioned purposes. Development of high-sensitivity and high-through put technology for the in situ monitoring of T-cell responses during vaccination against cancer by measuring serial gene expression levels by quantitative Real-Time PCR and by cDNA microarray technology. With these techniques we are actively investigating variables involved in the algorithm modulating tumor/host interactions in the context of active vaccination protocols.